Traditionally, sunglasses comprise eyeglasses that employ lenses that are tinted to reduce the amount of light that passes through the lenses. This reduction in light intensity makes the lens useful by reducing eyestrain in bright circumstances, and saves the user from squinting when in brightly lit areas, such as the out-of-doors on bright, sunny days.
Sunglasses are tinted a variety of colors. Some have a brownish tint, others have a greenish tint. Other colors have also been used.
One feature that many sunglasses include is that they possess a “polarized” lens. Polarized lenses were originally invented by Edwin Land, who also invented the Polaroid Camera. The purpose of a polarized lens is to eliminate an orientation of glare. Depending upon how the lens is positioned (oriented), one can eliminate glare at any angle. If the lens is rotated about its axis, it can move from a point wherein it eliminates vertical glare, to a point when rotated 90, where it eliminates horizontal glare. Most sunglasses are designed to eliminate horizontal glare, as this is the glare that tends to be most bothersome to the user when viewing things in bright light.
Horizontally polarized glare is the type of glare that is usually created when light reflects off a surface such as the surface of a water body or a road. The horizontally polarized light is blocked by vertical polarizers in the lens.
There are several ways that lenses can be tinted to have a color imparted to them. One way that lenses can be tinted is by mixing a color into the plastic from which a plastic lens is molded. Another way to make a tinted lens is to dye a colorant into a lens after the lens is molded.
Although sunglass lenses can be made of glass, most sunglass lenses today are made of some type of plastic. Many better sunglass lenses are made from a polycarbonate material that has desirable durability and optical clarity properties.
One of the better methods for making polarized tinted sunglasses is to introduce a tinted polarized film material, such as a green polarizing film into an injection mold cavity. The plastic stock material (e.g. polycarbonate) is then injected into the injection mold cavity on either side of the film, so that when finished, the polarized tinted film is sandwiched between two layers of polycarbonate. A hardening material can then be placed over the exterior surface of the polycarbonate material to make the lens more scratch resistant.
Most lenses are tinted a single uniform color throughout the lens. As such, the lens will have the same tinting at the top of lens as it will at the bottom; the same at the left side, as it will at the right side. Such lenses perform their function well, and are generally easy to produce by the process described above.
Another type of tinted lens is a gradient lens, wherein the color of the lens varies from one side of the lens to the other.
In a typical gradient lens, the lens is tinted to be darker toward the top of the lens, and lighter toward the bottom of the lens. This type of gradient has value because the darker top portion of the lens will tend to tint out the greatest source and quantity of glare, which is typically the sun overhead, while providing a less tinted area in the lower portion of the lens that enables the user to read through the bottom portion of the lens. As such, this typical type of gradient lens is analogous to a bifocal clear lens, in that it divides the lens into two zones. Whereas a bifocal lens will typically divide a lens into a far distance lens at the top and a close reading lens at the bottom, the gradient lens will divide the lens into a relatively more glare or light-blocking portion in the top portion and a relatively more light transmissive portion in the bottom portion.
Gradient lenses are usually not manufactured by the technique described above for single-color lenses. Rather, gradient lenses are typically made by dying the lens with a liquid dye that causes the lens to take on the desired color. In order to get the gradient effect, the lens is dipped into a vat of coloring materials “upside down”, so that the bottom of the finished lens is closer to the top of the surface of the immersion tank. At the beginning of the cycle, the lens will often be totally immersed within the dye solution and is held in the tank with a fixture. Over time, the fixture that holds the lens raises the lens out of the dye solution. This process causes the top of the finished lens (that, as described above, is positioned closer to the bottom of the dye vat) to remain within the dye for a longer period of time than the bottom of the finished lens. By remaining immersed in the dye for a longer period of time, the top of the lens can absorb more dye, and hence, can be tinted to a darker color.
By contrast, the bottom of the finished lens (which of course is placed closer to the upper surface of the dye in the vat), is the first part of the lens to be removed from its immersion in the dye, as the jig or fixture raises the lens upwardly out of the dye vat. As such, the bottom of the finished lens spends less time within the dye, and therefore, absorbs less dye. A result thereof is the bottom portion is not tinted to as deep (dark) of a color as the top of the lens.
Unfortunately, there is an important drawback to using a dying process for creating sunglasses. This drawback is that polarized glasses can not be made through a dying process, as described above. Rather, achieving a polarized lens is currently achievable by using the film process or coating, since the film or coating contains the “polarizers” necessary for the creation of a polarized lens. As such, although a dying process can be employed to create a gradient sunglass lens, it can not be used to create a gradient polarized sunglass lens. Further, polarized coatings are not durable over time.
Different types of lenses are more or less useful for different types of circumstances and user preferences.
Gray tinted lenses have the benefit of trapping all wavelengths of color generally equally. As such, gray lenses are often preferred because they maintain the natural colors that the user is viewing, although the intensity (or brightness) of the colors is reduced. The intensity of color is reduced because a user viewing the world through a pair of gray lenses sees less brightness because the sunglasses absorb the wavelengths and reduce the intensity of the light entering the user's eyes.
Lenses that are tinted in colors other than gray tend to have selective absorption characteristics that filter certain wavelengths of light a greater degree than they filter other wavelengths. For example, amber colored glasses tend to filter out a greater percentage of blue light out than red light. Some users value the blue blocking propensities of amber glasses, because blue light, being at the edge of a visible spectrum, tends to causes more eye strain than other wavelengths of light, such as red light. As such, amber lenses enhance the comfort of the user, because they block out a greater percentage of the most irritating blue light wavelengths than lenses of other colors. The user using an amber pair of sunglass lenses views the world through a tint of distorted colors, with the blue tones being less prominent and the red tones being highlighted.
The Applicant has found that green tinted polarized glasses are especially valuable for certain water-related activities, and especially fishing-related activities. A green polarized lens is valuable for fishermen because a green lens will tend to allow green light to pass through the lens while filtering out other colors to a much greater extent and eliminating glare from the surface of the water. This has the result of highlighting green objects that the user views.
When fishing, and especially when fishing in freshwater, many of the objects that a fisherman is looking for are green in color. These green objects include such things as weed lines, and certain fish species. Most freshwater fish have a greenish tint to them, with certain desired species such as bass, and bluegill being predominantly green. The use of green lenses thereby helps fishermen to spot fish in the water more easily, and also to spot things such as weed lines. Being able to spot weed lines enables the fishermen to better choose a location in the water at which to throw their fishing lines and hooks.
Because of these properties of green lenses, the Applicant has had significant success selling such green polarized tinted lenses to fishermen.
However, another factor that must be considered when designing a pair of sunglasses is not just the color of lens chosen, but the particular shade and depth of color chosen. A darker shaded lens tends to filter out more light, and a lighter shaded lens tends to filter out less light. Although this enhanced filtering out of light by darker lenses does have a benefit in bright sunshine, it also has the drawback of making it more difficult for the user to see objects appropriately in less well-lit circumstances, such as when the user is fishing in the shadows, or at dusk or early morning when less light is available.
By contrast, a lighter shade of lens, while beneficial to the user in low light conditions, may not block enough light in highly intense conditions to prevent discomfort to the user or prevent him from squinting.
One factor that exacerbates this issue is that during a session of fishing, the fisherman will often move from shadowy areas to the lighted areas on a fairly regular basis. This movement will occur both because the fisherman decides to move location, and also because clouds moving overhead will block the sun from time to time. This cloud movement can change a well lit area into a shadowed area as the clouds pass between the user and the sun. Further, as time passes, shadows will increase or decrease as the position of the sun moves relative to the foliage around the pond.
To overcome this problem, many fishermen carry two pairs of sunglasses with them while fishing. It is not unusual for a fisherman to wear a pair of lanyards around her neck, with each lanyard being coupled to a different pair of sunglasses. One of the pair of sunglasses is typically shaded very darkly to provide desired light blockage when the fisherman is in bright sun, and the second pair will be colored more lightly, and will be worn when the fisherman is in a shadowed area. Being forced to carry around two pair of sunglasses on a pair of lanyards represents both an additional expense to the user, and also an inconvenience.
It is therefore one object of the present invention to produce sunglass lenses that contain a relatively more darkened first portion to block out bright sun, and a second portion that is relatively lighter tinted to enable the fisherman to see well in low light conditions.
It is a second object of the present invention to provide a lens wherein both the darker portion and the relatively lighter portion are both polarized, to help reduce glare.